A major discovery about mammalian brains surprises researchers

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Summary: V-ATPase, a vital enzyme that powers neurotransmission, can randomly turn on and off, even over long periods of time.

Source: University of Copenhagen

Researchers at the University of Copenhagen have made an incredible discovery in a new breakthrough in understanding more about the mammalian brain. Namely, a vital enzyme that provides brain signals turns on and off randomly, even taking “breaks” for hours.

These findings could have major implications for our understanding of the brain and the development of pharmaceuticals.

It’s on the cover of Discovery Today nature🇧🇷

Millions of neurons are constantly communicating with each other to form thoughts and memories and allow us to move our bodies the way we want them to. When two neurons meet to exchange a message, neurotransmitters are transported from one neuron to another with the help of a unique enzyme.

This process is crucial for neuronal communication and the survival of all complex organisms. Until now, researchers around the world thought that these enzymes were constantly active to transmit important signals. But this is far from the case.

Using an innovative method, researchers from the Department of Chemistry at the University of Copenhagen took a closer look at the enzyme and discovered that its activity switches on and off at random intervals, which contradicts our previous understanding.

“This is the first time anyone has studied these mammalian brain enzymes one molecule at a time, and we are amazed by the results. Contrary to popular belief and unlike many other proteins, these enzymes can stop working from minutes to hours. However, the brains of humans and other mammals can function miraculously,” says Professor Dimitrios Stamou, who led the study from the Center for Geometrically Engineered Cell Systems in the Department of Chemistry at the University of Copenhagen.

Until now, such studies have been conducted on stable enzymes rather than bacteria. Using a new method, researchers have for the first time studied mammalian enzymes isolated from rat brains.

The study is published today nature🇧🇷

Altering enzymes can have far-reaching implications for neuronal communication

Neurons communicate using neurotransmitters. To transmit messages between two neurons, neurotransmitters are first pumped into small membrane sacs (called synaptic vesicles). Urinary bladders act as receptacles for neurotransmitters, releasing them only when it’s time to deliver a message between two neurons.

The enzyme central to this study, known as V-ATPase, is responsible for providing energy for the neurotransmitter pumps in these vessels. Without this, neurotransmitters would not be injected into the containers, and the containers would not be able to transmit messages between neurons.

But research shows that each container contains only one enzyme; when this enzyme is turned off, there is no more energy left to drive the loading of neurotransmitters into the containers. This is a completely new and unexpected discovery.

“It is almost incomprehensible that the extremely critical process of loading neurotransmitters into containers is entrusted to only one molecule per container. Especially when we found that 40% of the time these molecules are turned off,” says Professor Dimitrios Stamou.

This indicates v-atpases in the synaptic vesicle
Cover image shows vacuole-type adenosine triphosphatases (V-ATPases, large blue structures) in a synaptic vesicle from a nerve cell in the mammalian brain. Image: C. Kutzner, H. Grubmüller and R. Jahn/Max Planck Institute for Multidisciplinary Sciences. Credit: C. Kutzner, H. Grubmüller and R. Jahn/Max Planck Institute for Multidisciplinary Sciences.

These findings raise many interesting questions:

“Does shutting off the energy source of the containers mean that most of them are really empty of neurotransmitters? Can a large proportion of empty containers significantly affect the connectivity between neurons? If so, could this be a “problem” that neurons have evolved to circumvent, or could it be an entirely new way to encode important information in the brain? Only time will tell,” he says.

A revolutionary method to screen drugs for V-ATPase

The V-ATPase enzyme is an important drug target because it plays a critical role in cancer, cancer metastasis, and several other life-threatening diseases. Thus, V-ATPase is a lucrative target for anticancer drug development.

Current assays for drug screening for V-ATPase are based on simultaneous averaging of signals from billions of enzymes. Knowing the average effect of the drug is sufficient as long as one enzyme is continuously working at the right time, or as long as a large number of enzymes are working together.

“However, we now know that neither is necessarily true for V-ATPase. As a result, it suddenly became critical to have methods that measure the behavior of individual V-ATPases to understand and optimize the desired effect of a drug,” said first author Dr. Elefterios Kosmidis, Department of Chemistry, University of Copenhagen, who led experiments in the lab.

The method developed here is the first to measure the effect of drugs on the proton pumping of single V-ATPase molecules. It can detect currents over a million times smaller than the gold standard patch clamp method.

Facts about the enzyme V-ATPase:

See also

This shows a diagram of the gut and brain
  • V-ATPases are enzymes that break down ATP molecules to pump protons across cell membranes.
  • They are found in all cells and are important for controlling pH/acidity inside and/or outside the cell.
  • The proton gradient established by the V-ATPase in neuronal cells provides energy for the loading of neurochemical messengers called neurotransmitters into synaptic vesicles for subsequent release at synaptic junctions.

This is about neurological research news

Author: Press Service
Source: University of Copenhagen
Contact: Press office – University of Copenhagen
Image: The image is in the public domain

Original Research: Closed entrance.
🇧🇷Regulation of mammalian-brain V-ATPase by ultraslow mode switching” Dimitrios Stamou et al. nature


Regulation of mammalian-brain V-ATPase by ultraslow mode switching

Vacuolar-type adenosine triphosphatases (V-ATPases) are electrogenic rotary mechanoenzymes structurally related to F-type ATP synthases. They hydrolyze ATP to create an electrochemical proton gradient for a plethora of cellular processes.

In neurons, the loading of all neurotransmitters into synaptic vesicles is powered by approximately one V-ATPase molecule per synaptic vesicle. To shed light on this bona fide single-molecule biological process, we investigated electrogenic proton pumping by single mammalian-brain V-ATPases in single synaptic vesicles.

Here we show that V-ATPases are not pumped in time, as suggested by observing the rotation of bacterial homologs and assuming strict ATP-proton coupling.

Instead, they stochastically switch between three ultralong-lived modes: proton-pumping, inactive, and proton-leaking. In particular, direct observation of the pump revealed that physiologically relevant concentrations of ATP did not regulate the intrinsic pump rate.

ATP regulates V-ATPase activity through proton-pump mode switching probability. In contrast, electrochemical proton gradients regulate the pumping rate and the switching of pumping and inactive modes.

A direct consequence of mode switching is an all-or-none stochastic fluctuation in the electrochemical gradient of synaptic vesicles, which is expected to introduce stochasticity in the proton-driven secondary active loading of neurotransmitters, and thus may have important implications for neurotransmission.

This work uncovers and highlights the mechanistic and biological significance of ultraslow mode switching.

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